Digital encoded audio & video information is stored on disks in form of pits. These pits are spiral grooves. These pits originate from the disk’s center and run through to its edges. Other side of pits is read by the help of laser in order to read and execute the program or movie which has been recorded on the DVD media disk. The pits on the DVD disk have to be more closely packed and smaller in size to store more information. The reading laser has to be more precise in order to read data from the smaller pits. DVD media uses red-laser while blue-laser is used in the new Blu-ray media disc format. This is how the Blu-ray got its name because of the blue laser. Red laser has 650 nanometers wavelength. On the other hand the wavelength of blue laser is much shorter which 405 nanometers is. Smaller sized laser beam can focus more accurately and precisely.

The blue laser has the ability to read to read data from the pits that have size of 0.15 µm (microns). One micron is equivalent to 10-6 meters. The pits on the DVD disk are twice as bigger than that of the pits on Blu-ray media disc. Track pitch in the DVD disc is 0.74 microns which has been reduced to 0.32 microns in the Blu-ray media disk. The shorter track pitch, smaller laser beam and smaller pits, all these features assist the Blu-ray disk to record data of 25-GB on a single layer. Now the users have more luxury as the recording capacity of Blu-ray media disk is 5 times more than DVD disk.

The thickness of DVD and Blu-ray disk is same. The thickness of both disks is 1.2 millimeters. The data recording procedure is different for both disk types. DVD disc has 2 polycarbonate layers and the thickness of each layer is 0.6 mm. The information which is to be recorded on DVD disk is sandwiched between these 2 layers. A layer on top of the recorded information can lead to birefringence. In birefringence, the laser light is refracted into 2 separate beams by the substrate layer. Data cannot be read from the DVD disk if the laser light splits too wide. Disk tilt is another problem that is caused if the surface of DVD disc is not totally flat or it is not precisely perpendicular to the laser the light. The laser beam distorts due to disk tilt. Very involved manufacturing procedure is required in DVD disk to avoid these problematic issues.

These problems have been solved in the Blu-ray disk format. In Blu-ray disk format, the data is recorded on top of polycarbonate layer whose thickness is 1.1 mm. This technique of Blu-ray overcomes birefringence. So as a result the readability problems are avoided in the Blu-ray disk format. In Blu-ray disc format, the objective lens and the recording layer are very closer to each other.

This closeness to the objective lens virtually eliminates the disk tilt problem which enhances the performance. The outer side of Blu-ray media disk is protected by a hard coating because the recorded information is very closer to the blu-ray disk’s surface. This hard coating feature makes the Blu-ray media unique, robust, efficient and more advantageous. The hard coating layer protects the Blu-ray disk surface from fingerprints and scratches. Therefore, the Blu-ray media disc is able to store information for longer time periods. Blu-ray media format is more reliable and robust.